1. Technical Field
The present invention relates to a locking mechanism for a nail gun. More particularly, the present invention relates to a nail pusher slidably formed in a magazine of a nail gun, a lockout element of which the sliding movement on the nail pusher is restricted, and a pushing arm that pushes a nail according to the nail pusher.
2. Related Art
A locking mechanism of a nail gun, namely, an empty-nail shooting blocking mechanism, is to automatically inspect whether the magazine and the drive track are empty when the multiple nails are exhausted while operating a nail gun. The locking mechanism also makes the trigger stay in an invalid pressing and driving state, so that the user cannot drive the shooting action and be reminded to replenish the nails.
The traditional locking mechanism of a nail gun as disclosed in Taiwanese Patent No. 3221044 includes a fixed lockout element formed on a side surface of a nail pusher in a magazine. The stopping member moves to block the slider element together with the nail pusher at a displacement of a thickness of a single nail when the last nail is shot out of the nail gun. The shooting operation is thus stopped. As the thickness of the currently used nail is about 0.6 mm to 1.2 mm, the displacement to block the slider element is only 0.6 mm to 1.2 mm. Therefore, the stopping surface area is insufficient. When the user forces pressing the slider element without knowing that the drive track is empty, the slider element is easily detached from the blocking of the lockout element, so as to affect the shooting blocking effect of the nail gun.
In Taiwanese Patent No. 1283625 and U.S. Pat. No. 7,513,403, a more advanced locking mechanism mounted on a nail pusher that uses a moveable lockout element to stop a slider element is disclosed. A lockout element is slidably formed on a side surface of a nail pusher by resilient force. When the last nail in the drive track is gone, the lockout element resiliently shifts towards the drive track with a displacement larger than the thickness of a single nail, so as to block the movement of the slider element. Consequently, the nail shooting operation of the nail gun is stopped. However, because a sliding gap is respectively formed between the nail pusher and the interior wall of the magazine and between the lockout element and the nail pusher, the nail pusher and the lockout element become loosened after a long operation time. The loosened lockout element is easily stocked in the interior wall of the magazine to affect the smooth operation thereof. Also, the slider element may be possibly detached from the blocking of the lockout element to affect the operation. Besides, both locking mechanisms are not triggered by the existence of last nail(s). Instead, they are actually triggered by the relative location of the slider element and the nail pusher. To make sure it's a zero nail lockout, the slider element has to be sensitive to such as a 0.6 mm movement of the nail pusher in order to not lockout with one nail. This requires very tight tolerance control. To overcome this drawback, U.S. Pat. No. 7,182,236 provides a spring and a lockout element located on the nail pusher.
In Taiwanese Patent No. M269156, a moveable lockout element to block the movement of a slider element is disclosed. A touch element is formed on the nail pusher, and a pendulum lockout element is pivotally formed on the side surface of the magazine. The nail pusher moves towards the drive track with a displacement of the thickness of a single nail when the last nail in the drive track is gone. Thereby, the touch element pushes the lockout element to incline out of the magazine and to the moving path of the slider element, such that the movement of the slider element is blocked. However, when the lockout element inclines out of the magazine, the area to block the slider element is the cross sectional area of the inclination of the lockout element, and a force component is generated because of the inclination, such that the lockout element may be pushed back to the non-blocking position by the safety slid rod. Therefore, the blocking stability to the slider element is affected.